The slider with automatic lock means for a slide fastener generally has a stop member provided with an engaging pawl adapted to be resiliently protruded into the fastener chain passage channel formed in the slider body under the action of a leaf spring incorporated on the upper surface of the slider body. The stop member is required to be so designated that it smoothly engages and releases the slider in response to an external force applied to the pull tab of the slider within a predetermined resiliency range set. If the resiliency of the stop member is excessively high, the force required to release the stop member from engagement with the chain becomes too high for the pull tab to be manually operated. On the other hand, when the resiliency of the stop member is insufficient, the engaging force with which the stop member engages the chain is too low and, as a result, the slider is easily released even when only a slight external force is applied to the stop means and the slider is maintained under its unstable stopping condition. Therefore, the spring for the stop member is required to have a repulsing force within a predetermined range.
The fastener slider with automatic lock means generally incorporates a leaf spring and the rotary shaft of the pull tab within the space defined between the upper surface of the slider body and a cover secured to the slider body. And various resilient engaging constructions for sliders have been proposed. For example, in one resilient engaging construction, the engaging pawl is formed by bending the leading end of the leaf spring itself and the engaging pawl is caused to protrude into the fastener chain passage channel formed in the slider body. In another resilient engaging construction, an engaging pawl is formed at the side edge of the cover and caused to protrude into the fastener chain passage channel to thereby anchor the slider. Either of the prior art resilient slider engaging constructions is produced by in succession incorporating a plurality of different components such as a pull tab, a spring and a cover on the upper surface of the slider body and an acceptable fastener slider product can be obtained only when the components are precisely shaped and dimensioned and function properly and are properly assembled together.
However, it has been difficult to perfectly prevent the production of unacceptable fastener sliders because of varying factors such as variations in production conditions and materials and variations in processing conditions such as part supply and assembly. Therefore, the conventional inspection of such fastener sliders has been exclusively conducted by manual operation to reject unacceptable products from the production line.
Of late, fastener sliders with automatic lock means have been produced by continuous automatic high speed production, and in order to enhance the production efficiency, it has become necessary to perform the inspection step in the production operation automatically and especially as one step of a continuous production scheme. The present invention has been developed to meet this requirement.